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"Why is the EoS for tin so soft?" is a longstanding question, which prevents us from determining the nuclear incompressibility $K_\infty$ accurately. To solve this puzzle, a fully self-consistent quasiparticle random phase approximation (QRPA) plus quasiparticle-vibration coupling (QPVC) approach based on Skyrme-Hartree-Fock-Bogoliubov is developed. We show that the many-body correlations introduced by QPVC, which shift the ISGMR energy in Sn isotopes by about 0.4 MeV more than the energy in $^{208}$Pb, play a crucial role in providing a unified description of the ISGMR in Sn and Pb isotopes. The best description of the experimental strength functions is given by SV-K226 and KDE0, which are characterized by incompressibility values $K_\infty=$ 226 MeV and 229 MeV, respectively, at mean field level.

We present recent results on the structure of the one-valence-particle $^{41}$Ca and $^{49}$Ca, and one-valence-hole $^{47}$Ca, nuclei. The isotopes of interest were populated via the cold-neutron capture reactions $^{40}$Ca(n,$\gamma$), $^{48}$Ca(n,$\gamma$) and $^{46}$Ca(n,$\gamma$), respectively. The experiments were performed at the Institut Laue-Langevin, within the EXILL campaign, which employed a large array of HPGe detectors. The $\gamma$ decay and level schemes of these nuclei were investigated by $\gamma$-ray coincidence relationships, leading to the identification of 41, 10, and 6 new transitions in $^{41}$Ca, $^{47}$Ca, and $^{49}$Ca, respectively. Branching ratios and intensities were extracted for the $\gamma$ decay from each state, and $\gamma$-ray angular correlations were performed to establish a number of transition multipolarities and mixing ratios, thus helping in the spin assignment of the states. The experimental findings are discussed along with microscopic, self-consistent beyond-mean-field calculations performed with the Hybrid Configuration Mixing model, based on a Skyrme SkX Hamiltonian. The latter suggests that a fraction of the low-spin states of the $^{41}$Ca, $^{49}$Ca, and $^{47}$Ca nuclei is characterized by the coexistence of either 2p-1h and 1p-2h excitations, or couplings between single-particle/hole degrees of freedom and collective vibrations (phonons) of the doubly-magic "core".

The direct $\gamma$-decays of the giant dipole resonance (GDR) and the giant quadrupole resonance (GQR) of $^{208}$Pb to low-lying states are investigated by means of a microscopic self-consistent model. The model considers effects beyond the linear response approximation. The strong sensitivity of $\gamma$-decay to the isospin of the involved states is proven. By comparing their decay widths, a much larger weight of the $3_{1}^{-}$ component in the GQR wave function of $^{208}$Pb is deduced, with respect to the weight of the $2_{1}^{+}$ component in the GDR wave function. Thus, we have shown that $\gamma$-decay is a unique probe of the resonance wave functions, and a testground for nuclear structure models., Comment: 6 pages, 3 figures

The goal of nuclear structure physics is to provide a complete understanding of the static properties of atomic nuclei, their excitation spectra, their response to external fields and their decays. While it is hard to achieve these goals within a single framework, so that there is no nuclear ‘standard model’, it is clear that nuclear Density Functional Theory (DFT) has probably the widest range of applicability so far. In this paper, we try to put DFT in a broader context, with frequent comparisons to electronic DFT. We also include a discussion of the relationships with ab initio methods and Effective Field Theories (EFTs) in general, as well as a short survey of the quite large number of applications. Although written with a personal and possibly biased perspective, the paper aims at fostering cross-fertilizations with other domains of science.

The first 2^{+} and 3^{-} states of the doubly magic nucleus ^{132}Sn are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The ^{132}Sn ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a ^{206}Pb target. Deexciting γ rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0_{g.s.}^{+}→2_{1}^{+}, 0_{g.s.}^{+}→3_{1}^{-}, and 2_{1}^{+}→3_{1}^{-} in ^{132}Sn. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2;0_{g.s.}^{+}→2_{1}^{+}) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of ^{132}Sn. ispartof: PHYSICAL REVIEW LETTERS vol:121 issue:25 ispartof: location:United States status: published

6 pags., 4 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0, The first 2(+) and 3(-) states of the doubly magic nucleus Sn-132 are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The Sn-132 ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a Pb-206 target. Deexciting gamma rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0(g.s)(+) -> 2(1)(+), 0(g.s)(+) -> 3(1)(-), and 2(1)(+) -> 3(1)(-) in Sn-132. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2; 0(g.s)(+) -> 2(1)(+)) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of Sn-132., The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 654002. This work was supported by the German BMBF under Contract No. 05P15PKCIA and Verbundprojekt No. 05P2015, in part by the High Performance Computing Infrastructure Strategic Program (Grant No. hp150224), in part by MEXT and Joint Institute for Computational Fundamental Science and a priority issue (elucidation of the fundamental laws and evolution of the universe) to be tackled by using the Post “K” Computer (Grants No. hp160211 and No. hp170230), in part by the HPCI system research project (Grant No. hp170182), by the CNS-RIKEN joint project for large-scale nuclear-structure calculations, in part by the Spanish Ministry of Economy, Industry and Competitiveness through Project No. FPA2017-87568-P, by FWO-Vlaanderen (Belgium), by GOA/2010/010 (BOF KU Leuven), and by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12). A. V. and L. K. thank the Bonn-Cologne Graduate School of Physics and Astronomy for financial support. J. P. and D. M. C. acknowledge the Academy of Finland (Contract No. 265023). G. R. acknowledges support by Bulgarian National Science Fund under Grant No. DN08/23/16. L. P. G. has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska- Curie Grant Agreement No. 665779.

The information on the symmetry energy and its density dependence is deduced by comparing the available data on the electric dipole polarizability αD of 68Ni, 120Sn, and 208Pb with the predictions of the random-phase approximation, using a representative set of nuclear energy density functionals. The calculated values of αD are used to validate different correlations involving αD, the symmetry energy at the saturation density J , the corresponding slope parameter L, and the neutron skin thickness rnp, as suggested by the droplet model. A subset of models that reproduce simultaneously the measured polarizabilities in 68Ni, 120Sn, and 208Pb are employed to predict the values of the symmetry energy parameters at saturation density and rnp. The resulting intervals are J =30-35 MeV, L=20-66 MeV; and the values for rnp in 68Ni, 120Sn, and 208Pb are in the ranges 0.15-0.19, 0.12-0.16, and 0.13-0.19 fm, respectively. The strong correlation between the electric dipole polarizabilities of two nuclei is instrumental to predict the values of electric dipole polarizabilities in other nuclei.

The isoscalar monopole response has been measured in the unstable nucleus (68)Ni using inelastic alpha scattering at 50A MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1 ± 1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9 ± 1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L = 0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

The experimental study of the {Delta}{ital T}{sub {ital z}}=+1 component of the isovector monopole resonance of {sup 208}Pb has revealed itself as an experimental puzzle. We present in this work a theoretical calculation of the strength distribution of this resonance and of its neutron decay properties, within the framework of a model in which random phase approximation states are coupled with continuum configurations and with a set of {open_quote}{open_quote}doorway states{close_quote}{close_quote} in order to describe the basic escape and damping mechanisms of the nuclear vibration. Our results are compared with existing measurements and with other theoretical analyses. {copyright} {ital 1996 The American Physical Society.}

The γ decays of neutron-rich Ca isotopes around 48Ca were measured at Legnaro National Laboratory with the PRISMA-CLARA setup, using the heavy-ion transfer reactions 48Ca on 64Ni and 48Ca on 208Pb at ≈6 MeV/A. The work shows the feasibility to perform full in-beam γ spectroscopy with heavy-ion transfer reactions (in terms of angular distributions, polarizations, and lifetimes analysis), providing a method that can be further exploited in the future with heavy targets and radioactive beams. For the one-neutron transfer channels, 49Ca and 47Ca, shell-model and particle-vibration coupling calculations are used to understand the nature of the states. In particular, in both nuclei evidence is found for particle-vibration coupled states based on the 3− phonon of 48Ca. In the two-neutron transfer channels, 46Ca and 50Ca, the experimental data are in global agreement with predictions based on full fp shell-model calculations.

The isospin character, the collective or single-particle nature, and the sensitivity to the slope of the nuclear symmetry energy of the low-energy isovector dipole response (known as pygmy dipole resonance) are nowadays under debate. In the present work we study, within the fully self-consistent non-relativistic mean field (MF) approach based on Skyrme Hartree-Fock plus Random Phase Approximation (RPA), the measured even-even nuclei ${}^{68}$Ni, ${}^{132}$Sn and ${}^{208}$Pb. To analyze the model dependence in the predictions of the pygmy dipole strength, we employ three different Skyrme parameter sets. We find that both the isoscalar and the isovector dipole responses of all three nuclei show a low-energy peak that increases in magnitude, and is shifted to larger excitation energies, with increasing values of the slope of the symmetry energy at saturation. We highlight the fact that the collectivity associated with the RPA state(s) contributing to this peak is different in the isoscalar and isovector case, or in other words it depends on the external probe. While the response of these RPA states to an isovector operator does not show a clear collective nature, the response to an isoscalar operator is recognizably collective, for {\it all} analyzed nuclei and {\it all} studied interactions., Comment: Submitted to Phys. Rev. C

NESTER PTH; We have used the 43 MeV/nucleon primary tritium beam of the AGOR facility with an intensity of 4×107 pps and the BBS experimental setup to study the (t,3He) reaction between 0° and 5° lab angles on 12C, 48Ca, and 58Ni targets. The standard ray-tracing procedure has allowed us to obtain excitation-energy spectra up to 30 MeV in six angular bins for each residual nucleus, with an average energy resolution of 350 keV. The reaction mechanism has been described in distorted-waves Born approximation (DWBA) using the DWBA98 code. In this approximation, the form factor is treated as a folding of an effective projectile-nucleon interaction with a transition density. The effective projectile-nucleon interaction has been adjusted to reproduce the 0° cross section of the 1+ ground state of 12B populated in the 12C(t,3He) reaction. We have employed random-phase approximation (RPA) wave functions of excited states to construct the form factor instead of the normal modes wave functions used earlier. This new DWBA+RPA analysis is used to compare calculated and experimental cross sections directly and to discuss the giant resonance excitations in 48K and 58Co nuclei.

NESTER PTH